Electrooptical device, projection-type display apparatus, and method for manufacturing the electrooptical device

ABSTRACT

The present invention provides an electrooptical device wherein in a thin-film transistor (TFT) array substrate of the electrooptical device, a scanning line, a drain electrode, a first light shield layer, and a data line are laminated over a channel region of a TFT and a second light shield layer is laminated beneath the channel region. A side wall formation trench is formed beside the channel region of the TFT, and in the side wall formation trench a conductive layer having a light shield property is concurrently formed with the first light shield layer thereby a light shield side wall is formed. By three-dimensionally blocking the entry of light towards the channel region, obliquely or laterally incident light is prevented from entering the channel region of a pixel switching TFT, and the TFT is free from erratic operations and reliability degradation.

This application is a continuation of PCT/JP01/03359 filed Apr. 19,2001.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates to an active-matrix type electroopticaldevice, a projection-type display apparatus incorporating theelectrooptical device, and a method for manufacturing the electroopticaldevice. Particularly, the present invention relates to an electroopticaldevice having a pixel switching thin-film transistor (TFT) in a laminatestructure formed on a substrate thereof, a projection-type displayapparatus incorporating the electrooptical device as a light valve, anda manufacturing method for manufacturing the electrooptical device.

2. Description of Related Art

Active-matrix type electrooptical devices suffer from a change in TFTcharacteristics as a result of photocurrent leakage that occurs whenincident light enters a channel region of a pixel switching TFT in eachpixel. Since an electrooptical device for use as a light valve in aprojector uses a high-intensity light ray, blocking the admittance oflight into the channel region of the TFT and the peripheral area of thechannel region is important. A light shield layer, arranged on a countersubstrate, that defines an aperture area of each pixel, or a data line,fabricated of a metal layer such as Al (aluminum) running over the TFTon a TFT array substrate blocks the admittance of light into the channelregion or its peripheral area. A light shield layer, fabricated of arefractory metal, for example, is arranged on the TFT array substrate ina position facing the TFT from below. Such a light shield layer arrangedbeneath the TFT prevents light back-reflected from the TFT arraysubstrate from entering the TFT in the electrooptical device. Forexample, in an optical system that is composed of a plurality ofelectrooptical devices combined with a prism, such a light shield layerprevents returning light such as a light ray passing through the prismfrom another electrooptical device from entering the TFT in oneelectrooptical device of interest.

For example, such an electrooptical device, having high light-shieldperformance, can be used as a light valve in a projection-type displayapparatus which is subject to high-intensity light.

SUMMARY OF THE INVENTION

The above light shield techniques have the following disadvantages. Forexample, in the technique of using a light shield layer formed on acounter substrate or a TFT array substrate, the light shield layer andthe channel region are substantially spaced apart from each other with aliquid-crystal layer, an electrode, and an interlayer insulator that areinterposed therebetween. However, the light shield performance forblocking light that is obliquely incident on the area between the lightshield layer and the channel region is not sufficient enough. In acompact electrooptical device to use as a light valve in a projector,the incident light is a light beam into which a lens converges lightfrom a light source, and contains a significant component of obliquelyincident light (for example, 10% of the incident light is oblique by 10degrees to 15 degrees with respect to a direction normal to thesubstrate). Such insufficient light shield performance to the obliquelyincident light creates a problem in operation.

Light entering the electrooptical device through an area having no lightshield layer may be reflected off the top surface of the substrate, thetop surface of the light shield layer formed on the substrate, or theunderside of the data line, i.e., the inner surface of the data linefacing the channel region. The light reflected in this way may bereflected again off the top surface of the substrate, or the innersurfaces of the light shield layer and the data line, thereby causingmultiple reflections. The multiple reflections may reach the channelregion of the TFT.

As a demand for display image with higher quality in the electroopticaldevice increases, the electrooptical device has a higher definition anda finer pixel pitch. Furthermore, as incident light rays intensifies inlevel to present a brighter image, a variety of conventional lightshield techniques become unable to sufficiently block the admittance oflight. Stray light causes a change in transistor characteristics of theTFT, resulting in flickering and leading to degradation of the displayimage quality.

Expanding the formation area of the light shield layer has beencontemplated to increase light tightness. Expanding the formation areaof the light shield layer makes it difficult to increase the apertureratio of each pixel. It is noted that the aperture ratio needs to beincreased for a brighter display image. The light shield layer beneaththe TFT and the light shield layer (ex. a data line) over the TFT resultin internal reflections and multiple reflections of obliquely incidentlight rays. The expanding of the formation area of the light shieldlayer increases internal reflections and multiple reflections of lightand thus causes problems.

In view of at least the above problems, the present invention has beendeveloped. It is an object of the present invention to provide anelectrooptical device which features high light tightness, and presentsa bright and high-quality image, a projection-type display apparatusincorporating the electrooptical device, and a method for manufacturingthe electrooptical device.

To resolve the above problems, a first electrooptical device of thepresent invention includes a first substrate, a pixel electrode arrangedabove the first substrate, a thin-film transistor arranged above thefirst substrate and connected to the pixel electrode, and a first lightshield layer arranged over the gate electrode of the thin-filmtransistor formed over and facing the channel region of the thin-filmtransistor with a gate insulator interposed therebetween, wherein thefirst light shield layer is formed, laterally surrounding the channelregion as a light shield side wall.

In accordance with the first electrooptical device of the presentinvention, the first light shield layer deposited above the channelregion of the TFT prevents light coming in from the top side of thefirst substrate from entering the channel region. The first light shieldlayer, laterally surrounding the channel region as the light shield sidewall, prevents light from entering obliquely or laterally into thechannel region. Since the present invention prevents light coming infrom the top side of the first substrate from entering the channelregion of the TFT, the electrooptical device is free from erraticoperations of the TFT and a drop in reliability of the TFT.

In one embodiment, the first electrooptical device of the presentinvention can include a second substrate opposed to the first substrate,and an electrooptical material interposed between the first substrateand the second substrate. This embodiment presents a light-tightelectrooptical device, such as a liquid crystal device, having theelectrooptical material interposed between a pair of the substrates.

In another embodiment of the first electrooptical device of the presentinvention, a matrix of the pixel electrodes and the thin-filmtransistors can be arranged on the first substrate. In accordance withthis embodiment, an active-matrix type electrooptical device such as aliquid crystal device having high light tightness can be achieved.

In another embodiment of the first electrooptical device of the presentinvention, the light shield side wall can be formed of the first lightshield layer formed in a light shield side wall formation trench formedin an insulator below the first light shield layer.

The first electrooptical device having the above construction can bemanufactured using the following method. Specifically, a method formanufacturing an electrooptical device including a first substrate, apixel electrode arranged above the first substrate, and a TFT arrangedabove the first substrate and connected to the pixel electrode, includesforming, above the first substrate, the TFT including a channel region,a gate insulator formed on the channel region, and a gate electrode onthe gate insulator, with the gate electrode facing the channel regionwith the gate insulator interposed therebetween. The method can furtherinclude depositing at least one interlayer insulator covering the TFTsubsequent to the formation of the TFT, forming, in the interlayerinsulator, a side wall formation trench that runs by the side of thechannel region of the TFT, and depositing a first light shield layercovering at least the channel region of the TFT, wherein the first lightshield layer is also deposited in the side wall formation trench as alight shield side wall when the first light shield layer is formed.

In another embodiment of the first electrooptical device of the presentinvention, a drain electrode, formed over a drain region of the TFT, iselectrically connected to the drain region of the TFT, the pixelelectrode, formed over a drain electrode, is electrically connected tothe drain electrode, and the drain electrode is fabricated of aconductive layer having a light shield property formed over and coveringthe channel region. In this embodiment, besides the first light shieldlayer, the drain electrode having a light shield property blocks light,thereby reliably preventing light from entering the channel region.

In this embodiment, it is preferable that the drain electrode and thefirst light shield layer form a storage capacitor with an insulator, asa dielectric layer, interposed between the drain electrode and the firstlight shield layer preferably form a storage capacitor. In thisarrangement, each of the drain electrode and the first light shieldlayer is wide enough to cover the channel region. By using the insulatorinterposed therebetween as a dielectric layer, a storage capacitor isformed. This arrangement eliminates the need for routing a capacitiveline to each pixel, thereby increasing the aperture ratio of each pixel.

In another embodiment of the first electrooptical device of thisinvention, a data line formed over the source region of the TFT iselectrically connected to a source region of the TFT. Also, the dataline is fabricated of a conductive layer having a light shield propertyand covering the channel region from above. In this embodiment, besidethe first light shield layer, the data line having a light shieldproperty blocks light, thereby preventing light from entering thechannel region. In this embodiment, an active layer of the TFT ispreferably formed of a semiconductor layer that is arranged beneath thedata line and within the formation area of the data line.

In this arrangement, the data line having a light shield property blockslight to the entire semiconductor layer forming the TFT, and the TFT isformed within the formation area of the data line. The pixel apertureratio is thus increased. In this case, the data line extends in a linehaving an equal line width.

In another embodiment of the first electrooptical device of the presentinvention, a second light shield layer is laminated below the channelregion. Light, which is reflected off the first substrate or isreflected outside the first substrate and enters again the firstsubstrate from behind, is blocked by the second light shield layer inthis arrangement. The electrooptical device is free from erraticoperations of the TFT and a drop in reliability of the TFT, which can becaused when the reflected light enters the channel region of the TFT.

In this embodiment, preferably, the first light shield layer is routedthrough the side wall formation trench and is electrically connected tothe second light shield layer.

Since the channel region of the TFT is entirely laterally surrounded bythe first light shield layer, the light shield side wall, and the secondlight shield layer in this arrangement, light coming in from anydirection is reliably blocked. Since the first light shield layer andthe second light shield layer are electrically connected to each other,fixing the second light shield layer to a potential automatically fixesthe first light shield layer to the same potential. The first lightshield layer is easily used as a fixed-potential capacitive electrode ofa storage capacitor.

In this case, the first light shield layer may be directly connected tothe second light shield layer, or may be connected to the second lightshield layer through another conductive layer having a light shieldproperty. When the first light shield layer is connected to the secondlight shield layer through another conductive layer having a lightshield property, a conductive layer, fabricated of the same material asthe conductive layer forming the gate electrode, may be deposited on thebottom of the side wall formation trench, and the light shield side wallmay be formed on the conductive layer.

In the manufacturing of the first electrooptical device, a second lightshield layer, an underlayer insulator, a semiconductor layer forming thethin-film transistor, and a gate insulator of the thin-film transistorare deposited on the surface of the first substrate, prior to formationof the thin-film transistor on the top side of the first substrate.After forming a connection trench in the gate insulator and theunderlayer insulator, running by the side of the channel region of thethin-film transistor and reaching the second light shield layer, aconductive layer, which forms the gate electrode, is also deposited inthe connection trench when the gate electrode is produced. Theinterlayer insulator is deposited on the gate electrode, and then, theside wall formation trench is formed, communicating and being integralwith the connection trench when the side wall formation trench isformed. Subsequently, the first light shield layer is deposited, andwhen the first light shield layer is deposited, the first light shieldlayer also be formed in the side wall formation trench to form the lightshield side wall connected to the conductive layer in the side wallformation trench.

When the first light shield layer is directly connected to the secondlight shield layer, the first light shield layer may be formed in theside wall formation trench reaching the bottom thereof.

In manufacturing the electrooptical device in this arrangement, a secondlight shield layer, an underlayer insulator, a semiconductor layerforming the thin-film transistor, a gate insulator of the thin-filmtransistor, and a gate electrode of the thin-film transistor aredeposited on the surface of the first substrate, prior to formation ofthe thin-film transistor on the surface of the first substrate. Theinterlayer insulator is deposited on the gate electrode. The side wallformation trench is formed in the interlayer insulator, the gateinsulator, and the underlayer insulator, running by the channel regionof the thin-film transistor and reaching the second light shield layer.Subsequently, the first light shield layer is then deposited, and whenthe first light shield layer is deposited, the first light shield layeralso be formed in the side wall formation trench to form the lightshield side wall connected to the second light shield layer in the sidewall formation trench.

To resolve the previously described problem, a second electroopticaldevice of the present invention can include, above a substrate, a pixelelectrode, a thin-film transistor connected to the pixel electrode, awiring connected to the thin-film transistor, and a light shield memberthree-dimensional covering the thin-film transistor and the wiring.

In the second electrooptical device of the present invention, thethin-film transistor connected to the pixel electrode performs switchingcontrol, thereby driving the pixel in an active-matrix driving method.The light shield layer three-dimensionally covers the thin-filmtransistor. The light shield member prevents light rays entering thesubstrate vertically or obliquely from above, returning light raysentering the substrate vertically or obliquely from below, andinternally reflected light or multiple reflected light in response tothese light rays from entering the channel region of the thin-filmtransistor and the adjacent area of the channel region. The light shieldmember accurately defines the non-aperture area of each pixel in a gridconfiguration.

As a result, the second electrooptical device of the present inventionincreases light tightness, and allows a thin-film transistor withreduced photocurrent leakage to perform correctly switching control on apixel electrode under severe operational conditions in whichhigh-intensity light and returning light are present. The presentinvention thus presents a bright and high-contrast image.

In view of such technical effects, the light shield memberthree-dimensionally covering the thin-film transistor and the wiring, ina narrow sense, can mean a light shield member defining athree-dimensionally closed space which contains the thin-film transistorand the wiring, and in a broader sense, can mean a light shield memberdefining a three-dimensionally closed space with a slight opening ordiscontinuity which contains the thin-film transistor and the wiring aslong as the light shield member blocks (reflects or absorbs) lightcoming in three-dimensionally from various directions to some degree.

In another embodiment of the second electrooptical device of thisinvention, the light shield member can include one light shield layerdeposited on the bottom surface and the side wall of a trench formed inthe substrate and accommodating the thin-film transistor and the wiring,and another light shield layer covering the trench from above.

In this arrangement, the trench is formed in the substrate, and the onelight shield layer is deposited on the bottom surface and the side wallof the trench. The thin-film transistor and the wiring are placed in thetrench in a manner that the thin-film transistor and the wiring areinsulated from each other with an interlayer insulator interposedtherebetween or are insulated from the one light shield layer. Anotherlight shield layer covers the trench from above. With a relativelysimple construction and manufacturing process, the thin-film transistorand the wiring are three-dimensionally shielded from light.

In yet another embodiment of the second electrooptical device of thepresent invention, the light shield member can include a lower lightshield layer deposited above the substrate, an upper light shield layerdeposited above the thin-film transistor and the wiring, formed on thelower light shield layer, and a side wall light shield layer filling agroove formed from the upper light shield layer to the lower lightshield layer outside the thin-film transistor and the wiring in a planview.

In this embodiment, the thin-film transistor and the wiring are arrangedbetween the lower light shield layer and the upper light shield layer ina manner that the thin-film transistor and the wiring are insulated fromeach other with an interlayer insulator interposed therebetween or areinsulated from the lower light shield layer and the upper light shieldlayer. The groove can be formed in the interlayer insulator outside thethin-film transistor and the wiring, for example, extending from theupper light shield layer to the lower light shield layer, and the sidewall light shield layer fills the trench. With a relatively simpleconstruction and manufacturing process, the thin-film transistor and thewiring are three-dimensionally shielded from light.

In another embodiment of the second electrooptical device of thisinvention, the light shield member can include in one plane areathereof, one light shield layer deposited on the bottom surface and theside wall of a trench formed in the substrate and accommodating thethin-film transistor and the wiring, and another light shield layercovering the trench from above, and in another plane area, a lower lightshield layer deposited on the substrate, an upper light shield layerdeposited on the thin-film transistor and the wiring, formed on thelower light shield layer, and a side wall light shield layer filling agroove formed from the upper light shield layer to the lower lightshield layer outside the thin-film transistor and the wiring in a planview.

In this embodiment, a relatively wide trench can be formed in the oneplane area, and the one light shield layer is deposited on the bottomsurface and the side wall of the trench. The thin-film transistor andthe wiring are arranged within the trench in a manner that the thin-filmtransistor and the wiring are insulated from each other with aninterlayer insulator interposed therebetween or are insulated from theone light shield layer. Another light shield layer covers the trenchfrom above. In another area, the thin-film transistor and the wiring arearranged between the lower light shield layer and the upper light shieldlayer in a manner that the thin-film transistor and the wiring areinsulated from each other with an interlayer insulator interposedtherebetween or are insulated from the lower light shield layer and theupper light shield layer. A relatively narrow groove is formed in theinterlayer insulator outside the thin-film transistor and the wiring,extending from the upper light shield layer to the lower light shieldlayer, and the side wall light shield layer fills the groove. With arelatively simple construction and manufacturing process, the thin-filmtransistor and the wiring are reliably three-dimensionally shielded fromlight. By changing the material of the light shield member from area toarea, more flexibility can be provided in device design.

In another embodiment of the second electrooptical device of thisinvention, the light shield member can include one light shield layerdeposited on the bottom surface and the side wall of a trench formed inthe substrate and partly accommodating the thin-film transistor and thewiring, an upper light shield layer deposited above the thin-filmtransistor and the wiring formed above the one light shield layer, and aside wall light shield layer filling a groove formed from the upperlight shield layer to the one light shield layer outside the thin-filmtransistor and the wiring in a plan view.

In this embodiment, a relatively wide trench is formed in the substrate,and the one light shield layer is deposited on the bottom surface andthe side wall of the trench, and the thin-film transistor and the wiringare partly accommodated in the trench. The thin-film transistor and thewiring are accommodated in the trench in a manner that the thin-filmtransistor and the wiring are insulated from each other with aninterlayer insulator interposed therebetween or are insulated from theone light shield layer so that a part of the thin-film transistor andthe wiring is set to be higher in level than the edge of the trench withrespect to the substrate. The upper light shield layer is arranged onthe thin-film transistor and the wiring partly accommodated in thetrench. A relatively narrow groove is formed from the upper light shieldlayer to the one light shield layer outside the thin-transistor and thewiring, and the side wall light shield layer fills the groove. With arelatively simple construction and manufacturing process, the thin-filmtransistor and the wiring are reliably three-dimensionally shielded fromlight. By fabricating the light shield member of a plurality of lightshield layers, more flexibility is provided in device design.

To resolve the above-referenced problem, a third electrooptical deviceof the present invention can include a pair of first and secondsubstrates with an electrooptical material interposed therebetween, andabove the first substrate, a plurality of pixel electrodes arrangedtwo-dimensionally including a first pixel electrode group which isdriven in an alternating driving method with a first period and a secondpixel electrode group which is driven in an alternating driving methodwith a second period complimentary to the first period, a thin-filmtransistor connected to each pixel electrode, a wiring connected to eachthin-film transistor, and a light shield member which covers thethin-film transistor and the wiring in a gap area between adjacent pixelelectrodes in a plan view and protrudes in a ridge a portion of the gaparea between adjacent pixel electrodes of different pixel electrodegroups, and further includes above the second substrate, a counterelectrode facing the plurality of pixel electrodes.

In accordance with the third electrooptical device of the presentinvention, the thin-film transistor connected to the pixel electrodeperforms switching control on the pixel electrode in an active matrixdriving method. The first pixel electrode group is driven in analternating driving method with the first period while the second pixelelectrode group is driven in an alternating driving method with thesecond period which is complementary to the first period. In this way,the electrooptical device may be driven in a scanning line alternatingdriving method, in which the driving voltage to each pixel is alternatedin polarity every scanning line, or may be driven in a data linealternating driving method, in which the driving voltage to each pixelis alternated in polarity every data line, or may be driven in a dotalternating driving method, in which the driving voltage to each pixelis alternated in polarity every pixel. The use of the line alternatingdriving method serves the purpose of controlling degradation of theelectrooptical material caused by the application of a direct currentvoltage. Furthermore, cross-talk and flickering are also controlled on apresented display image. The light shield layer three-dimensionallycovers the thin-film transistor and the wiring in the gap area betweenthe adjacent pixel electrodes. The light shield member prevents lightrays entering the substrate vertically or obliquely from above,returning light rays entering the substrate vertically or obliquely frombelow, and internally reflected light or multiple reflected light inresponse to these light rays from entering the channel region of thethin-film transistor and the adjacent area of the channel region. Thelight shield member accurately defines the non-aperture area of eachpixel in a grid configuration.

The light shield member protrudes in a ridge a portion of the gap areabetween adjacent pixel electrodes of different pixel electrode groups.When the electrooptical device is driven in one of the line alternatingdriving methods, a transverse electric field taking place between theadjacent pixel electrodes of different driving voltage polarities isrelatively weakened. If a transverse electric field occurs between theadjacent pixel electrodes in the electrooptical device, which istypically driven by a longitudinal electric field between each pixelelectrode and the counter electrode, an operational fault is created inthe electrooptical material, such as a orientation defect of the liquidcrystal. In accordance with the present invention, the light shieldmember shortens the distance between the pixel electrode and the counterelectrode in the area where such a transverse electric field takesplace, thereby intensifying the longitudinal electric field in this areaand relatively weakening the adverse effect of the transverse electricfield in the same area.

As a result, the third electrooptical device of the present inventionincreases light tightness and allows a thin-film transistor with reducedphotocurrent leakage thereof to perform correctly switching control onthe pixel electrode under severe operational conditions in whichhigh-intensity light and returning light are present. The presentinvention adopts the line alternating driving method, which is effectivein lengthening the life of the electrooptical material and reducingflickering. The present invention thus presents a bright andhigh-contrast image.

In accordance with the third electrooptical device of the presentinvention, the light shield member includes, in an area between adjacentpixel electrodes of the same pixel electrode group, one light shieldlayer deposited on the bottom surface and the side wall of a trenchformed in the substrate and accommodating the thin-film transistor andthe wiring and another light shield layer covering the trench fromabove. The light shield member also includes, in an area betweenadjacent pixel electrodes of the different pixel electrode groups, alower light shield layer deposited on the substrate, an upper lightshield layer deposited on the thin-film transistor and the wiring,formed on the lower light shield layer, and a side wall light shieldlayer filling a groove formed from the upper light shield layer to thelower light shield layer outside the thin-film transistor and the wiringin a plan view.

In this embodiment, a relatively wide trench is formed in the firstsubstrate in the gap area between the pixels where no transverseelectric field takes place, and the one light shield layer is depositedon the bottom surface and the side wall of the trench. The thin-filmtransistor and the wiring are accommodated in the trench in a mannerthat the thin-film transistor and the wiring are insulated from eachother with an interlayer insulator interposed therebetween or areinsulated from the one light shield layer. Another light shield layercovers the trench from above. In the gap area between the pixelelectrodes where a transverse electric field takes place, the thin-filmtransistor and the wiring are arranged between the lower light shieldlayer and the upper light shield layer in a manner that the thin-filmtransistor and the wiring are insulated from each other with aninterlayer insulator interposed therebetween or insulated from the lowerand upper light shield layers.

A relatively narrow groove is formed in the interlayer insulator outsidethe thin-film transistor and the wiring, extending from the upper lightshield layer to the lower light shield layer. The side wall light shieldlayer fills the groove. In the gap area where the transverse electricfield takes place, the presence of the light shield member causes theridge in a localized position, thereby weakening the adverse effect ofthe transverse electric field. At the same time, in the gap area whereno transverse electric field takes place, the presence of the lightshield member causes no ridge, thereby reducing the operational faultdue to the orientation defect of the liquid crystal, which may be causedby a step at the underlayer beneath the pixel electrode on the firstsubstrate in contact with the electrooptical material.

In another embodiment, a planarizing process is performed on theunderlayer beneath the pixel electrode in the area between the adjacentpixel electrodes of the same pixel electrode group.

In this arrangement, the light shield member is arranged in the gap areawhere no transverse electric field is generated, but the underlayer ofthe pixel electrode is subjected to the planarizing process. Forexample, the planarizing process is performed by using a CMP (ChemicalMechanical Polishing) process, or a spin coating process, or by changingthe depth of the trench which accommodates the thin-film transistor andthe wiring. As a result, in the gap area where no transverse electricfield is generated, the operational fault such as the orientation defectof the liquid crystal, which may be caused by a step at the underlayerof the pixel electrode in contact with the electrooptical material, issubstantially reduced.

In the second and third electrooptical devices of the present invention,in which the light shield member includes the side wall light shieldlayer, the upper light shield layer and the lower light shield layer maybe integrally formed. In this arrangement, with a relatively simpleconstruction and manufacturing process, a highly reliable light shieldlayer is formed. After forming the groove in the interlayer insulatorwhich is laminated subsequent to the thin-film transistor or the wiring,the upper light shield layer may fill the groove.

In another embodiment of the second and third electrooptical devices ofthe present invention, the pixel electrode and the thin-film transistorare connected to each other through a conductive layer having a lightshield property. In this embodiment, a contact hole is opened, forexample, and light ingress is reliably prevented at the junction pointbetween the pixel electrode and the thin-film transistor, where aninternal space enclosed by the light shield member is likely to sufferfrom light ingress from outside.

In another embodiment of the second and third electrooptical devices ofthe present invention, the junction point between the pixel electrodeand the thin-film transistor is positioned at the center of adjacentthin-film transistors in a plan view. Even if light enters through thejunction point, for example the contact hole, between the pixelelectrode and the thin-film transistor into the internal space enclosedby the light shield member, the light ingress point is spaced from eachthin-film transistor along the surface of the substrate. Accordingly,stray light reaching the channel region of the thin-film transistor andthe adjacent area thereof is substantially reduced.

In another embodiment of the second and third electrooptical devices ofthe present invention, the electrooptical device includes a light shieldlayer facing the substrate and facing the junction point between thepixel electrode and the thin-film transistor. In this embodiment, acontact hole is opened, for example, and light ingress is reliablyprevented at the junction point between the pixel electrode and thethin-film transistor, where an internal space enclosed by the lightshield member is likely to suffer from light ingress from outside.

In another embodiment of the second and third electrooptical devices ofthe present invention, the light shield member can be formed of a filmcontaining a refractory metal. In this embodiment, the light shieldmember is formed of a single metal layer, an alloy layer, a metalsilicide layer, a polysilicide layer, or a multilayer of these layers,each of which layer is fabricated of at least one of the refractorymetals such as Ti (titanium), Cr (chromium), W (tungsten), Ta(tantalum), Mo (molybdenum), and Pb (lead). The light shield member thusprovides high light-shield performance.

In another embodiment of the second and third electrooptical devices ofthe present invention, the wiring can include scanning lines and datalines intersecting each other, and the light shield member is configuredin a grid in a plan view. In this embodiment, the scanning lines and thedata lines intersect each other in a grid configuration in an imagedisplay area. The light shield member having a grid configurationthree-dimensionally covers the grid configuration of the scanning linesand the data lines. This arrangement reduces the possibility that lightstrays into the thin-film transistors connected to the scanning linesand the data lines through the vicinity of each of the scanning linesand the data lines.

In another embodiment of the second and third electrooptical devices ofthe present invention, the electrooptical device can further include astorage capacitor formed in a space three-dimensionally covered with thelight shield member on the first substrate, and connected to the pixelelectrode. In this embodiment, the storage capacitor is formed within aspace three-dimensionally enclosed by the light shield member. Thestorage capacitor prevents light shield performance from dropping whileadding a capacitance to the pixel electrode. The voltage holdingcapability of each pixel electrode is thus increased.

To resolve the previously described object, a projection-type displayapparatus can include a light valve including one of the first, second,and third electrooptical devices as mentioned above (and themodifications thereof), a light source for directing light to the lightvalve, and an optical system for projecting a light beam from the lightvalve.

In the projection-type display apparatus of the present invention, thelight source directs light to the light valve, and the optical systemprojects a light beam from the light valve to a screen. The light valvecan be formed of one of the first, second, and third electroopticaldevices. With the above-discussed high lightshield performance, thethin-film transistor with reduced photocurrent leakage thereof reliablyperforms switching control on the pixel electrode under a high-intensityprojection light beam. As a result, the present invention thus presentsa bright and high-contrast image.

These operations and other advantages of the present invention willbecome more apparent from the following discussion of the embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, in which like elements are referred to with like numbers, andin which:

FIG. 1 is an equivalent circuit diagram of a variety of elements andwiring formed in each of a plurality of pixels arranged in a matrix inthe electrooptical device in accordance with the present invention;

FIG. 2 is a plan view showing a plurality of pixel groups adjacent toeach other in a TFT array substrate in which a data line, a scanningline, a pixel electrode, and a light shield layer are formed in theelectrooptical device of FIG. 1;

FIG. 3 is an enlarged view showing the formation area of the pixels inthe TFT array substrate of FIG. 2;

FIG. 4 is an enlarged view showing the formation area of the scanningline and the data line in the TFT array substrate of FIG. 2;

FIG. 5 is an enlarged view showing the formation area of a semiconductorlayer for forming a TFT in the TFT array substrate of FIG. 2;

FIG. 6 is a cross-sectional view showing the TFT array substrate takenalong line A—A′, line B—B′, and line C—C′ in FIG. 2;

FIG. 7 is an enlarged view showing the formation area of a drainelectrode in the TFT array substrate of FIG. 2;

FIG. 8 is an enlarged view showing a first light shield layer and theformation area of a side wall formation trench in the TFT arraysubstrate of FIG. 2;

FIG. 9 is an enlarged view showing the first light shield layer and theformation area of the side wall formation trench in the TFT arraysubstrate of FIG. 2;

FIG. 10 is a cross-sectional view showing a process of manufacturing theTFT array shown in FIG. 2;

FIG. 11 is a cross-sectional view showing a process to be performedsubsequent to the process shown in FIG. 10, for manufacturing the TFTarray shown in FIG. 2;

FIG. 12 is a cross-sectional view showing a process to be performedsubsequent to the process shown in FIG. 1, for manufacturing the TFTarray shown in FIG. 2;

FIG. 13 is a cross-sectional view showing a process to be performedsubsequent to the process shown in FIG. 12, for manufacturing the TFTarray shown in FIG. 2;

FIG. 14 is a cross-sectional view showing a process to be performedsubsequent to the process shown in FIG. 13, for manufacturing the TFTarray shown in FIG. 2;

FIG. 15 is a cross-sectional view showing a process to be performedsubsequent to the process shown in FIG. 14, for manufacturing the TFTarray shown in FIG.2;

FIG. 16 is a cross-sectional view showing a process to be performedsubsequent to the process shown in FIG. 15, for manufacturing the TFTarray shown in FIG.2;

FIG. 17 is a cross-sectional view of the electrooptical device of asecond embodiment of the present invention;

FIG. 18 is a plan view showing a plurality of pixel groups adjacent toeach other in a TFT array substrate having a data line, a scanning line,and a pixel electrode, thereon in an electrooptical device of a thirdembodiment;

FIG. 19 is a cross-sectional view of the TFT array substrate taken alongline D—D′ in FIG. 18;

FIG. 20 is a cross-sectional view of the TFT array substrate taken alongline E—E′ in FIG. 18;

FIG. 21 is a cross-sectional view of the TFT array of a fourthembodiment at a section corresponding to that taken along line E—E′ inFIG. 18;

FIG. 22 is a cross-sectional view of the TFT array of a fifth embodimentat a section corresponding to that taken along line E—E′ in FIG. 18;

FIG. 23 is a plan view of a plurality of pixel electrodesdiagrammatically showing the relationship between the polarity of adriving voltage in each pixel electrode and a generation area of atransverse electric field in an electrooptical device of a sixthembodiment of the present invention in a scanning line alternatingdriving operation;

FIG. 24 is a plan view showing the electrooptical device viewed from acounter substrate;

FIG. 25 is a cross-sectional view of the electrooptical device takenalong line H—H′ in FIG. 24;

FIG. 26 is a block diagram showing a circuit arrangement of aprojection-type display apparatus as one example of electronic equipmentincorporating the electrooptical device of the present invention as adisplay apparatus; and

FIG. 27 is a cross-sectional view showing an optical system of theprojection-type display apparatus as electronic equipment incorporatingthe electrooptical device of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The best mode for carrying out the present invention is now discussed,referring to the embodiments together with the drawings. In each of thefollowing embodiments, the electrooptical device of the presentinvention is employed in a liquid crystal device.

An electrooptical device of the first embodiment is now discussed,referring to FIG. 1 through FIG. 16.

The construction and operation of the electrooptical device of thepresent invention are discussed, referring to FIG. 1 through FIG. 9. Asshown, layers and members are not necessarily drawn to equal scale toshow the layers and members in easy-to-identify sizes.

Referring to FIG. 1, each of a plurality of pixels arranged in a matrixforming an image display area of the electrooptical device of thisembodiment includes pixel electrodes 9 a and TFT 30s for controlling thepixel electrodes 9 a, and data lines 6 a for supplying image signals areelectrically connected to the sources of the TFT 30s. Image signals S1,S2, . . . , Sn may subsequently be supplied to the data. lines 6 a onone line at a time basis or may be supplied to a plurality of adjacentdata lines 6 a on a group by group basis. Scanning lines 3 a arerespectively electrically connected to the gates of the TFTs 30, and aresupplied with scanning signals G1, G2, . . . , Gm in a pulse form, inthis order, on one line at a time basis. The pixel electrodes 9 a areelectrically connected to the drains of the TFTs 30, and turn on theTFTs 30 as switching elements for a predetermined period, therebywriting the image signals S1, S2, . . . , Sn supplied from the datalines 6 a, in each pixel at a predetermined timing. The image signalsS1, S2, . . . , Sn at a predetermined level written through pixelelectrodes 9 a on the liquid crystal as one example of electroopticalmaterial are held with respect to a counter electrode formed on acounter substrate, to be discussed later.

The electrooptical device modulates light to present a gradation displayby changing the orientation or order of a set of molecules with anapplied voltage level. In the normally white mode, transmittance ratioto incident light drops in response to the applied voltage while in thenormally black mode, the transmittance ratio to the incident light risesin response to the applied voltage. The liquid-crystal display deviceoutputs light having a contrast responsive to the image signal.

To prevent the stored image signal from being leaked, a storagecapacitor 70 may be added in parallel with a capacitance of the liquidcrystal formed between the pixel electrode 9 a and the counterelectrode. For example, the voltage at the pixel electrode 9 a ismaintained by the storage capacitor 70 for a period of time three ordersof magnitude longer than the period throughout which the source voltageis applied. The voltage holding characteristic of the pixel is thusimproved, and a high-contrast electrooptical device 100 can be achieved.

Referring to FIG. 2, the TFT array substrate of the electroopticaldevice includes a matrix of transparent pixel electrodes 9 a in eachpixel. The formation area of the pixel electrode 9 a is a rectangulararea hatched with upwardly inclined lines in an enlarged view in FIG. 3.

The data line 6 a and the scanning line 3 a run vertically andhorizontally, respectively, along the border area of each pixelelectrode 9 a, but unlike conventional electrooptical devices, nodedicated capacitive lines are formed.

The formation area of the data line 6 a is represented by an areahatched with downwardly inclined lines in the enlarged view in FIG. 4.Both edge portions of the data line 6 a overlap the edge of each pixelelectrode 9 a. The formation area of the scanning line 3 a isrepresented by an area hatched with upwardly inclined lines in theenlarged view in FIG. 4, and both edge portions of the scanning line 3 aoverlap the edge of each pixel electrode 9 a.

In this embodiment, the data line 6 a is electrically connected to thesource region, to be discussed later, of a semiconductor layer 1 aformed of a polysilicon layer through a contact hole 5. The pixelelectrode 9 a is electrically connected to the drain region, to bediscussed later, of the semiconductor layer 1 a through contact holes 81and 82. The scanning line 3 a (a gate electrode) runs facing the channelformation region, to be discussed later, of the semiconductor layer 1 a.

The formation area of the semiconductor layer 1 a is represented by anarea hatched with upwardly inclined lines in the enlarged view in FIG.5.

In this embodiment, the data line 6 a can be formed of a conductivelayer having a light shield property and extending in a line having anequal line width such as a metal layer of aluminum and an alloy layer ofmetal silicide. The semiconductor layer 1 a is formed beneath the dataline 6 a and within the formation area of the data line 6 a.Specifically, the semiconductor layer 1 a is arranged in the border arearunning vertically and horizontally between the pixel electrodes 9 a.

Referring to FIG. 6, the electrooptical device 100 includes a TFT arraysubstrate 10 (a first substrate) and a counter substrate 20 (a secondsubstrate) opposed to the TFT array substrate 10. The TFT arraysubstrate 10 is fabricated of a quartz substrate, for instance, and thecounter substrate 20 is fabricated of a glass substrate or a quartzsubstrate, for instance. The TFT array substrate 10 is provided with thepixel electrodes 9 a, and arranged on top of them is an alignment layer(not shown) which has been subjected to a predetermined alignmentprocess such as a rubbing process. The pixel electrode 9 a is fabricatedof a transparent conductive thin film, such as an ITO (Indium Tin Oxide)film. The alignment layer is fabricated of an organic thin film, such asa polyimide thin film.

The TFT array substrate 10 includes a pixel switching TFT 30 forperforming switching control of each pixel electrode 9 a, formed rightbelow the data line 6 a. The TFT 30 has an LDD (Lightly Doped Drain)structure and includes the scanning line 3 a (the gate electrode), thechannel region 1 a′ of the semiconductor layer 1 a in which a channel isformed by the electric field of the scanning signals supplied from thescanning line 3 a, a dual-structured gate insulator 2 for insulating thescanning line 3 a from the semiconductor layer 1 a, the data line 6 a (asource electrode), the lightly doped source region 1 b (a source LDDregion) and the lightly doped drain region 1 c (a drain LDD region) ofthe semiconductor layer 1 a, and the heavily doped source region 1 d andthe heavily doped drain region 1 e of the semiconductor layer 1 a. Acorresponding one of the plurality of pixel electrodes 9 a iselectrically connected to the heavily doped drain region 1 e.

The source regions 1 b and 1 d as well as the drain regions 1 c and 1 eare doped with a n-type dopant or a p-type dopant, depending on which ofthe two channels, a n-channel or a p-channel, is produced in thesemiconductor layer 1 a. The n-channel TFT provides a fast operationalspeed and is frequently used as a pixel switching TFT.

The TFT 30 preferably has the above-mentioned LDD structure.Alternatively, the TFT 30 may have an offset structure in which noimpurity ion implantation is performed on the regions corresponding tothe lightly doped source region 1 b and the lightly doped drain region 1c. The TFT 30 may also have a self-aligned type TFT in which a high doseimpurity ion is implanted with a part of the gate electrode 3 a beingused as a mask, to form heavily doped source and drain regions in aself-alignment process. In this embodiment, the gate electrode (the dataline 3 a) of the TFT 30 is of a single gate structure in which a gateelectrode is interposed between the source and drain regions 1 b and 1e, but alternatively, more than one gate electrode may be interposedtherebetween. In this case, the same signal is applied to the gateelectrodes. With dual gates (double gates) or triple gates employed in aTFT, photocurrent leakage at junctions between the channel region andthe source region as well as between the channel region and the drainregion are prevented, and thereby a current during off period isreduced. If at least one of the gate electrodes has a LDD structure oran offset structure, the off current is reduced even more, and areliable switching element can be achieved.

In this embodiment, the data line 6 a (the source electrode) can beformed of a metal layer of aluminum, or an alloy layer of metalsilicide.

Arranged over the scanning line 3 a (the gate electrode) and the gateinsulator 2 is a first interlayer insulator 4 through which a contacthole 5 leading to the heavily doped source region 1 d and a contact hole81 leading to the heavily doped drain region 1 e are formed. A secondinterlayer insulator 7 a is arranged over the interlayer insulator 4,and a third interlayer insulator 7 b is formed over the secondinterlayer insulator 7 a. The data line 6 a (the source electrode) isformed on the second interlayer insulator 7 a, and is electricallyconnected to the heavily doped source region 1 d through the contacthole 5.

The pixel electrode 9 a is formed on the third insulator 7 b. In thisembodiment, to electrically connect the pixel electrode 9 a to theheavily doped drain region 1 e of the TFT 30, a drain electrode 11 isformed on the surface of the first interlayer insulator 4. The drainelectrode 11 is electrically connected to the heavily doped drain region1 e of the TFT 30 through the contact hole 81 in the first interlayerinsulator 4. A contact hole 82 is drilled through the second interlayerinsulator 7 a and the third interlayer insulator 7 b, and the pixelelectrode 9 a is thus electrically connected to the drain electrode 11through the contact hole 82. The pixel electrode 9 a is electricallyconnected to the heavily doped drain region 1 e of the TFT 30 throughthe drain electrode 11.

In this embodiment, the drain electrode 11 is fabricated of a conductivelayer having a light shield property, such as a doped silicon layer (apolysilicon intermediary electrode) which is formed to fully cover theheavily doped drain region 1 e and the channel region 1 a from above. Asrepresented by an area hatched with upwardly inclined lines in FIG. 7,the formation area of the drain electrode 11 extends along the data line6 a and the scanning line 3 a in a cross configuration in the borderarea of each pixel electrode 9 a from the intersection of the data line6 a and the scanning line 3 a.

Referring to FIG. 6, in this embodiment, a thin insulator 12 can bedeposited on the top surface of the drain electrode 11, and a firstlight shield layer 13 is laminated between the thin insulator 12 and thesecond interlayer insulator 7 a, covering the channel region 1 a′ of theTFT 30. In this embodiment, the first light shield layer 13 is formed ofa metal layer, an alloy layer, a metal silicide layer, each of whichlayers contains at least either one of titanium, chromium, tungsten,tantalum, molybdenum, palladium, and aluminum, or a conductive layerhaving a light shield property such as a doped silicon. The formationarea of the first light shield layer 13 is represented by an areahatched with downwardly inclined lines in FIG. 8. The first light shieldlayer 13 extends vertically and horizontally along the border area ofeach pixel electrode 9 a in a grid configuration, and is held at apotential common to the pixels.

The drain electrode 11 is formed below the first light shield layer 13,and the drain electrode 11 and the first light shield layer 13 areopposed to each other over a wide area with the thin insulator 12interposed therebetween. In this embodiment, the thin insulator 12 isused as a dielectric layer, and the storage capacitor 70 having thefirst light shield layer 13 and the drain electrode 11 as the electrodesthereof is thus provided.

In this embodiment, referring to FIG. 6, a second light shield layer 14is formed on the TFT array substrate 10 in such a manner that the secondlight shield layer 14 covers the channel region 1 a′ of the TFT 30 frombelow. The underlayer insulator 15 is deposited on the top surface ofthe second light shield layer 14. The formation area of the second lightshield layer 14 is represented by an area hatched with downwardlyinclined lines in FIG. 9.

In this embodiment, a side wall formation trench 16 penetrates the thininsulator 12 and the first interlayer insulator 4, laterally surroundingthe channel region 1 a′ of the TFT 30. Referring to FIG. 8, the sidewall formation trench 16 is formed along the outline of the first lightshield layer 13 within the formation area of the first light shieldlayer 13. The formation area of the side wall formation trench 16 isrepresented by an area hatched with downwardly inclined lines at a pitchsmaller than that of the hatch area of the first light shield layer 13.

The side wall formation trench 16 in this embodiment communicates with aconnection trench 161 penetrating the gate insulator 2 and theunderlayer insulator 15. The connection trench 161 is filled with aconductive layer 162 having a light shield property that is produced atthe same time that the scanning line 3 a (the gate electrode) isproduced. The side wall formation trench 16 is filled with a lightshield side wall 131 that is formed of a conductive layer having a lightshield property and produced at the same time when the first lightshield layer 13 is produced.

The channel region 1 a′ of the TFT 30 is light shielded by the scanningline 3 a, the drain electrode 11, the first light shield layer 13, andthe data line 6 a from above, by the second light shield layer 14 frombelow, and by the light shield side wall 131 in the side wall formationtrench 16 and the electrically conductive layer 162 in the connectiontrench 161 from sides.

Referring back to FIG. 6, the counter substrate 20 has a counterelectrode (common electrode) 21 extending on the entire surface thereof,and an alignment layer (not shown) therebeneath which has been subjectedto a predetermined alignment process such as a rubbing process. Thecounter electrode 21 is fabricated of a transparent conductive film suchas an ITO film. The alignment layer of the counter substrate 20 isfabricated of an organic thin film such as a polyimide thin film. Thereare times that a light shield layer 23 is arranged in a matrix on thecounter substrate 20 in an area other than the aperture area in eachpixel.

For this reason, incident light L1 from the counter substrate 20 cannotenter the channel region 1 a′, LDD regions 1 b and 1 c of thesemiconductor layer 1 a of the TFT 30. The light shield layer 23 has thefunction of improving contrast and preventing color mixing of colormaterials.

The TFT array substrate 10 and the counter substrate 20 are arrangedwith the pixel electrodes 9 a facing the counter electrode 21, and aliquid crystal 50 as an electrooptical material is encapsulated in aspace surrounded by a sealing material, to be discussed later, betweenthe TFT array substrate 10 and the counter substrate 20. Theliquid-crystal layer 50 takes a predetermined orientation state by thealignment layers with no electric field applied by the pixel electrode 9a. The liquid-crystal layer 50 is formed of a mixture of one or severaltypes of nematic electrooptical materials. The sealing material is anadhesive agent made of a thermal setting agent or a photo-setting agentfor bonding the TFT array substrate 10 to the counter substrate 20 alongthe edges thereof, and is mixed with spacers such as glass fiber orglass beads to keep a predetermined distance between the two substrates.

As discussed above referring to FIG. 1 through FIG. 9, the scanning line3 a, the drain electrode 11, the first light shield layer 13, and thedata line 6 a are arranged over the channel region 1 a′ and the LDDregions 1 b and 1 c of the TFT 30. Strong light rays entering from thecounter substrate 20 cannot reach the channel region 1 a. The channelregion 1 a′ and the LDD regions 1 b and 1 c of the TFT 30 are lightshielded by the second light shield layer 14 from below. Even if lightis reflected from the TFT array substrate 10 or light reflected from anexternal optical member enters the TFT array substrate 10 from the backof the TFT array substrate 10, the light is prevented from entering thechannel region 1 a.

Moreover, in this embodiment, even if strong light entering from thecounter substrate 20 is obliquely or laterally directed to the channelregion 1 a, and the LDD regions 1 b and 1 c, no such light is admittedinto the channel region 1 a because the lateral portions of the channelregion 1 a′ and the LDD regions 1 b and 1 c are light shielded by thelight shield side wall 131 in the side wall formation trench 16 and theconductive layer 162 in the connection trench 161.

Accordingly, even if a strong light ray enters from the countersubstrate 20, as in a projection-type display apparatus to be discussedlater, the electrooptical device 100 of this embodiment is free fromerratic operations of the TFT 30 and a drop in reliability of the TFT30, attributed to the admittance of light into the channel region 1 a′of the TFT 30.

In this embodiment, the drain electrode 11 electrically connected to thepixel electrode 9 a in each pixel and the first light shield layer 13common to all pixels are opposed to each other with the thin insulator12 interposed therebetween in a wide area. The first light shield layer13 and the second light shield layer 14 are electrically connected toeach other through the light shield side wall 131 in the side wallformation trench 16 and the conductive layer 162 in the connectiontrench 161. If the second light shield layer 14 is fixed to a potential,the first light shield layer 13 is fixed to the same potential. In thisembodiment, the storage capacitor 70 is formed by having the drainelectrode 11, the first light shield layer 13 as the capacitiveelectrodes thereof, and the thin insulator 12 as a conductive layer.Since this arrangement eliminates the need for routing a dedicatedcapacitive line to each pixel, the pixel aperture ration is increased.

The method of manufacturing the electrooptical device 100 of the firstembodiment having the above construction is now discussed, referring toFIG. 10 through FIG. 16.

The method of manufacturing the TFT array substrate 10 is now discussed.Referring to FIG. 10 through FIG. 16, there shown are cross-sectionalviews showing processes of manufacturing the TFT array substrate 10 ofthis embodiment. FIG. 10 through FIG. 16 show cross sections of the TFTarray substrate 10 corresponding to those taken along line A—A′, B—B′,and C—C′ in FIG. 2.

Referring to FIG. 10(A), a TFT array substrate 10 fabricated of a glasssubstrate or a quartz substrate, for instance, is prepared. The TFTarray substrate 10 is preferably annealed in an inert gas atmosphere,such as N₂ (nitrogen) gas, within a temperature range of 900 to 1300degrees Centigrade so that the TFT array substrate 10 suffers from lessdistortion in a subsequent high temperature thermal process. In otherwords, the TFT array substrate 10 is subjected beforehand to a heattreatment as high as or higher than the maximum temperature expected inthe high temperature thermal process in the manufacturing process.

A tungsten silicide layer 140 as the second light shield layer 14 isformed to be 200 nm thick. The tungsten silicide layer 140 is thenpatterned as shown in FIG. 10(B), thereby forming the second lightshield layer 14.

Formed on the TFT array substrate 10 is the underlayer insulator 15fabricated of a silicate glass film, such as NSG (non-silicate glass),PSG (phosphosilicate glass), BSG (borosilicate glass), or BPSG(borophosphosilicate glass), a silicon nitride film, or a silicon oxidefilm, using a TEOS (tetraethylorthosilicate) gas, a TEB (triethylborate) gas, or a TMOP (trimethyl phosphate) gas by an atmospheric CVDmethod or a reduced pressure CVD method. The thickness of the underlayerinsulator 15 is within a range from 500 to 2000 nm.

Referring to FIG. 10(C), an amorphous silicon layer 1 a″ is deposited onthe underlayer insulator 15 using a reduced pressure CVD (at a pressureof 20 to 40 Pa) with monosilane gas or disilane gas at a flow ratewithin a range from 400 cc/minute to 600 cc/minute in a relatively lowtemperature environment within a range from 450 degrees C. to 550degrees C., preferably at about 500 degree C. The TFT array substrate 10is subjected to an annealing process at a temperature within a rangefrom 600 degrees C. to 700 degrees C. for the duration from one hour toten hours, preferably for the duration from four to six hours in anitrogen atmosphere, and a polysilicon layer 1 is grown by solid-phaseepitaxy to a thickness within a range from 50 nm to 200 nm, preferablyto a thickness of approximately 100 nm.

When the pixel switching TFT 30 is of a P-channel type, the channelformation region may be doped with a small amount of Group V dopant,such as Sb (antimony), As (arsenic), or P (phosphorus), through an ionimplantation technique. When the pixel switching TFT 30 is of anN-channel type, the channel formation region may be doped with a smallamount of Group III dopant, such as B (boron), Ga (gallium), or In(indium), through an ion implantation technique. The polysilicon 1 maybe directly formed through the reduced pressure CVD rather than by wayof the amorphous silicon layer. The polysilicon layer deposited throughthe reduced pressure CVD is implanted with silicon ions to form anamorphous silicon layer, and the amorphous silicon layer is thenrecrystallized through an anneal process to form the polysilicon layer1.

Referring to FIG. 10(D), the semiconductor layer 1 a having the patternshown in FIG. 2 and FIG. 5 is formed through a photolithographic stepand an etching step.

Referring to FIG. 11(A), the semiconductor layer 1 a forming the TFT 30is thermally oxidized at a temperature within a range from 900 degreesCentigrade to 1300 degrees Centigrade, preferably at a temperature ofapproximately 1000 degrees Centigrade. A relatively thinthermally-oxidized silicon layer 201 as thin as 30 nm is then formed. Ahigh temperature oxide layer 202 (HTO layer) or a silicon nitride layeris deposited to a thickness of about 50 nm using the reduced pressureCVD. A gate insulator 2 having a multi-layer structure thus can beachieved. A gate insulator 2 having a single layer structure may bedeposited only through the thermal oxidation. After the formation of thegate insulator 2, the above-referenced ion implantation may beperformed.

Referring to FIG. 11(B), the connection trench 161 reaching the secondlight shield layer 14 is formed in the gate insulator 2 and theunderlayer insulator 15.

Referring to FIG. 11(C), a polysilicon layer 3 is deposited through thereduced pressure CVD, and is thermally diffused with phosphorus (P) tomake the polysilicon layer 3 conductive. A doped silicon layer may beused which is doped with P ions at the film formation phase of thepolysilicon layer 3.

Referring to FIG. 11(D), the scanning line 3 a (the gate electrode)having the pattern shown in FIG. 2 and FIG. 4 is formed through aphotolithographic step or an etching step using a resist mask. Thethickness of the scanning line 3 a is about 350 nm. The connectiontrench 161 is filled with a conductive layer 162 which is made from thesame material as the scanning line 3 a.

When the TFT 30 shown in FIG. 6 is of an n-channel TFT having a LDDstructure, the semiconductor layer 1 a is lightly doped with a Group Vdopant 200 such as P with the scanning line 3 a (the gate electrode) asa diffusion mask (with a dose of P ions falling within a range from1×10¹³/cm² to 3×10¹³/cm²) in order to form the lightly doped sourceregion 1 b and the lightly doped drain region 1 c in the semiconductorlayer 1 a as shown in FIG. 12(A). The semiconductor 1 a beneath thescanning line 3 a (the gate electrode) becomes the channel region 1 a′.With this impurity doping, the resistance of the scanning line 3 a isreduced.

After a resist mask 203 wider than the scanning line 3 a (the gateelectrode) is deposited on the scanning line 3 a (the gate electrode),the semiconductor layer 1 a is heavily doped with a Group V dopant 201such as P (for example, with a dose of P ions falling within a rangefrom 1×10¹⁵/cm² to 3×10¹⁵/cm²) in order to form the heavily doped sourceregion 1 d and the heavily doped drain region 1 e of the TFT 30 as shownin FIG. 12(B). The n-channel TFT may have an offset structure withoutimplanting a light dose of impurity.

When the TFT 30 is of a p-channel, the semiconductor layer 1 a is dopedwith a Group III dopant such as B in order to form the lightly dopedsource region 1 b, the lightly doped drain region 1 c, the heavily dopedsource region 1 d, and the heavily doped drain region 1 e in thesemiconductor layer 1 a. The TFT may have an offset structure withoutimplanting a light dose of impurity. A self-alignment TFT may beproduced using an ion implantation technique for P ions or B ions withthe scanning line 3 a (the gate electrode) as a mask. With this low-doseimpurity doping, the resistance of the scanning line 3 a is furtherreduced.

In parallel with these steps, peripheral circuits such as a data linedriving circuit and a scanning line driving circuit, respectively havinga complementary structure of a n-channel TFT and a p-channel TFT, areproduced on the periphery of the TFT array substrate 10. Since the pixelswitching TFT 30 is a polysilicon TFT in this embodiment, the peripheralcircuits such as the data line driving circuit and the scanning linedriving circuit are produced at substantially the same steps as thosefor the pixel switching TFTs. This feature is advantageous from themanufacturing process standpoint.

Referring to FIG. 12(C), the interlayer insulator 4 covering thescanning line 3 a (the gate electrode) of the TFT 30 is formed of asilicate glass film such as NSG, PSG, BSG, or BPSG, a silicon nitridefilm, or a silicon oxide film, using a TEOS gas by an atmospheric CVDmethod or a reduced pressure CVD method. The thickness of the interlayerinsulator 4 is preferably within a range from 500 to 1500 nm.

Referring to FIG. 12(D), the contact hole 81 for connecting the heavilydoped drain region 1 e to the drain electrode 11 is formed using a dryetching process such as a reactive ion etching or a reactive ion beametching, or a wet etching process.

Referring to FIG. 13(A), a polysilicon layer 110 is deposited to producethe drain electrode 11 on the surface of the first interlayer insulator4 by the reduced CVD method. The polysilicon layer 110 is thermallydiffused with phosphorus (P) to be conductive. Alternatively, a dopedsilicon layer may be used which is doped with P ions at the filmformation phase of the polysilicon layer 110.

Referring to FIG. 13(B), the drain electrode 11 having the pattern shownin FIG. 2 and FIG. 7 is produced through a photolithographic step and anetching step using a resist mask.

Referring to FIG. 13(C), a thin insulator 12 is deposited on the surfaceof the drain electrode 11.

Referring to FIG. 13(D), the side wall formation trench 16 for formingthe light shield side wall 131 using the first light shield layer 13 isformed in the thin insulator 12 and the first interlayer insulator 4 byusing a dry etching process, such as a reactive ion etching or areactive ion beam etching, in a way that the side wall formation trench16 communicates with the connection trench 161. The side wall formationtrench 16 is then integrally formed with the connection trench 161.

Referring to FIG. 14(A), a tungsten silicide layer 130 for forming thefirst light shield layer 13 on the surface of the insulator 12 isdeposited to a thickness of about 200 nm. The tungsten silicide layer130 is patterned as shown in FIG. 14(B), thereby forming the first lightshield layer 13. The light shield side wall 131 is formed in the sidewall formation trench 16 at the same time that the first light shieldlayer 13 is produced, and is electrically connected to the layer 162 onthe bottom portion of the side wall formation trench 16.

Referring to FIG. 14(C), the second interlayer insulator 7 a is formed,comprising a silicate glass film, such as NSG, PSG, BSG, or BPSG, asilicon nitride film, or a silicon oxide film, using a TEOS gas by anatmospheric CVD method or a reduced pressure CVD method. The thicknessof the second interlayer insulator 7 a is preferably within a range from500 to 1500 nm.

Referring to FIG. 15(A), the contact hole 5 for the data line 3 a (thesource electrode) is formed using a dry etching process such as areactive ion etching or a reactive ion beam etching, or a wet etchingprocess.

Referring to FIG. 15(B), a metal layer 6 of a low-resistance metal suchas Al, or a metal silicide, is deposited on the second interlayerinsulator 7 a to a thickness falling within a range from 100 nm to 500nm, preferably, to a thickness of approximately 300 nm using asputtering technique.

Referring to FIG. 15(C), the data line 6 a (the source electrode) isproduced using a photolithographic step and an etching step.

Referring to FIG. 16(A), the third insulator 7 b covering the data line6 a (the source electrode) is formed, including a silicate glass filmsuch as NSG, PSG, BSG, or BPSG, a silicon nitride film, or a siliconoxide film, using a TEOS gas by an atmospheric CVD method or a reducedpressure CVD method. The thickness of the third insulator 7 b ispreferably within a range from 500 to 1500 nm.

Referring to FIG. 16(B), the contact hole 82 for electrically connectingthe pixel electrode 9 a to the drain electrode 11 is produced by using adry etching process such as a reactive etching or a reactive ion beametching.

Referring to FIG. 16(C), a conductive transparent layer 9 such as an ITOfilm is deposited on the third insulator 7 b to a thickness fallingwithin a range from 50 nm to 200 nm by using a sputtering technique.

The conductive transparent layer 9 is patterned through aphotolithographic step, and an etching step, thereby forming the pixelelectrode 9 a as shown in FIG. 6. Polyimide-based alignment liquid isapplied on the pixel electrode 9 a to form an alignment layer. A rubbingprocess is then performed on the alignment layer to impart apredetermined pretilt angle to the alignment layer.

The production of the TFT array substrate 10 of the electroopticaldevice 100 is now complete.

To produce the counter substrate 20 shown in FIG. 6, a glass substrateis first prepared. A light shield layer 23 on the counter substrate anda light shield layer 53 (see FIG. 24 and FIG. 25) as a frame forpartitioning a display area from a non-display area are produced bysputtering chromium and then through a photolithographic step, and anetching step. The counter substrate light shield layer 23 and the lightshield layer 53 as a frame are fabricated of a metal such as Cr, Ni, Al,or dispersed resin black in which carbon or Ti is mixed withphotoresist.

A conductive transparent layer such as an ITO layer is deposited on theentire surface of the counter substrate 20 to a thickness of 50 nm to200 nm through a sputtering technique. The counter electrode 21 is thusformed. Polyimide-based alignment liquid is applied on the pixelelectrode 9 a to form an alignment layer. A rubbing process is thenperformed on the alignment layer to impart a predetermined pretilt angleto the alignment layer. The formation of the alignment layer is thuscompleted.

The production of the counter substrate 20 of the electrooptical device100 is complete.

In this way, the TFT array substrate 10 and the counter substrate 20 arebonded together with the alignment layers facing each other using asealing member (not shown). Through vacuum absorption, an electroopticalmaterial including a mixture of a plurality of nematic electroopticalmaterials is drawn into the space between the two substrates. The liquidcrystal layer 50 having a predetermined thickness is thus obtained. Theproduction of the electrooptical device 100 of the first embodimentalready discussed with reference to FIG. 1 through FIG. 9 is thuscompleted.

The electrooptical device of a second embodiment of the presentinvention is now discussed, referring to FIG. 17. FIG. 17 is across-sectional view of an electrooptical device 100′ of the secondembodiment of the present invention.

The manufacturing method of the electrooptical device 100′ of the secondembodiment is different from the that of the electrooptical device 100of the first embodiment in that the process for forming the connectiontrench 161, as in the description of the first embodiment with referenceto FIG. 11(B), is eliminated and in that the side wall formation trench16 is formed to reach the second light shield layer 14 as shown in FIG.17 in the second embodiment in the formation step of the side wallformation trench 16 described in the first embodiment with reference toFIG. 13(D). The rest of the manufacturing process remains unchanged fromthat of the first embodiment.

With the electrooptical device 100′ manufactured as shown in FIG. 17,the light shield side wall 131 fabricated of the same material as thatof the first light shield layer 13 fills the side wall formation trench16 when the first light shield layer 13 is formed. The light shield sidewall 131 is directly in contact with the second light shield layer 14 onthe bottom of the side wall formation trench 16. The electroopticaldevice 100′ of the second embodiment has a TFT array substrate 10different from that included in the electrooptical device 100′ of thefirst embodiment shown in FIG. 6, and the rest of the construction isthe same as that of the electrooptical device 100′ of the firstembodiment as described with reference to FIG. 6. Therefore, thecorresponding elements are designated with the same reference numerals,and the discussion thereof is omitted.

The construction of the pixel of the electrooptical device in a thirdembodiment of the present invention is now discussed, referring to FIG.1 and FIG. 18 through FIG. 20. FIG. 18 is a plan view showing aplurality of pixel groups adjacent to each other in a TFT arraysubstrate having a data line, a scanning line, and a pixel electrode,formed thereon in an electrooptical device of the third embodiment. FIG.19 is a cross-sectional view of the TFT array substrate taken along lineD—D′ in FIG. 18. FIG. 20 is a cross-sectional view of a part of laminatestructure formed on the TFT array substrate taken along line E—E′ inFIG. 18. Referring to FIG. 19 and FIG. 20, layers and members are notnecessarily drawn to equal scale to show the layers and members ineasy-to-recognize sizes. In FIG. 18 through FIG. 20 showing the thirdembodiment, the components identical to those described with referenceto FIG. 1 through FIG. 9 showing the first embodiment are designatedwith the same reference numerals, and the discussion thereof is omittedas appropriate.

The basic construction of the circuit arrangement of the electroopticaldevice of the third embodiment remains substantially similar to that ofthe electrooptical device of the first embodiment shown in FIG. 1. Inthe first embodiment, the second light shield layer 14 has the functionof the capacitive line for fixing the fixed-potential capacitiveelectrode of the storage capacitor 70 to a fixed potential. In the thirdembodiment, a capacitive line overlaps and runs over the scanning line 3a.

Referring to FIG. 18 and FIG. 19, a capacitive line 300 including thefixed-potential capacitive electrode is arranged. Specifically, in aplan view, the capacitive line 300 extends in a stripe configurationalong the scanning line 3 a and juts upward and downward in a regionoverlapping the TFT 30 as shown in FIG. 18. The formation area of thestorage capacitor 70 is increased making use of the area over thescanning line 3 a and the area beneath the data line 6 a.

Referring to FIG. 18 through FIG. 20, the storage capacitor 70 in thethird embodiment is formed of an intermediary layer 71, as apixel-potential capacitive electrode, connected to the heavily dopeddrain region 1 e of the TFT 30 and to the pixel electrode 9 a, and of aportion of the capacitive line 300 as a fixed-potential capacitiveelectrode, arranged opposed to each other, with a dielectric layer 75interposed between the intermediary layer 71 and the portion of thecapacitive line 300.

The capacitive line 300, fabricated of a metal layer containing a metalor an alloy, functions as the fixed-potential capacitive electrode. Thecapacitive line 300 is formed of a single metal layer, an alloy layer, ametal silicide layer, a polysilicide layer, or a multilayer of theselayers, each of which layers comprises at least a refractory metal, suchas Ti, Cr, W, Ta, Mo, and Pb. The capacitive line 300 may have amulti-layer structure formed of a first layer fabricated of a conductivepolysilicon layer, and a second layer fabricated of a metal silicidelayer containing a refractory metal.

The intermediary layer 71, fabricated of a conductive polysilicon layer,functions as a pixel-potential capacitive electrode. Besides thefunction of the pixel-potential capacitive electrode, the intermediarylayer 71 has the function of electrically connecting the pixel electrode9 a to the heavily doped drain region 1 e of the TFT 30. Theintermediary layer 71 may also have a single layer structure containinga metal or an alloy or a multi-layer structure like the capacitive line300.

Referring to FIG. 18 and FIG. 20, a trench 10CV is formed in the TFTarray substrate 10 in a grid area coarsely hatched with downwardlyinclined lines in FIG. 18. A lower light shield layer 400 is arranged ina grid configuration within the trench 10CV. Like the capacitive line300, the lower light shield layer 400 is formed of a single metal layer,an alloy layer, a metal silicide layer, a polysilicide layer, or amultilayer of these layer, each of which layers comprises at least arefractory metal, such as Ti, Cr, W, Ta, Mo, and Pb.

In the grid area coarsely hatched with downwardly inclined lines shownin FIG. 18, an upper light shield layer 401 is arranged. Like the lowerlight shield layer 400, the upper light shield layer 401 is formed of asingle metal layer, an alloy layer, a metal silicide layer, apolysilicide layer, or a multilayer of these layer, each of which layerscomprises at least a refractory metal, such as Ti, Cr, W, Ta, Mo, andPb. Further, a narrow groove is formed along the outline of the upperlight shield layer 401, penetrating a fourth interlayer insulator 44, athird interlayer insulator 43, a dielectric layer 75, a secondinterlayer insulator 42, a first interlayer insulator 41, and anunderlayer insulator 40. A side wall light shield layer 402, filling thenarrow groove, extends from the upper light shield layer 401 to thelower light shield layer 400. The side wall light shield layer 402 isformed of a single metal layer, an alloy layer, a metal silicide layer,a polysilicide layer, or a multilayer of these layer, each of whichlayers comprises at least a refractory metal, such as Ti, Cr, W, Ta, Mo,and Pb. The lower light shield layer 400, the upper light shield layer401 and the side wall light shield layer 402 may be formed of the samelight shield layer or different light shield layers.

Referring to FIG. 19 and FIG. 20, elements and lines formed in the imagedisplay area of the TFT array substrate 10, such as the TFT 30, thescanning line 3 a, the data line 6 a, the capacitive line 300, and thestorage capacitor 70, are three-dimensionally light shielded by thelower light shield layer 400, the upper light shield layer 401, and theside wall light shield layer 402 in the third embodiment. Referring toFIG. 19, a conductive, light shield layer 403 is arranged in a contacthole 85 connecting the pixel electrode 9 a to the intermediary layer 71so that no light enters a space defined by the lower light shield layer400, the upper light shield layer 401 and the side wall light shieldlayer 402 through the vicinity of the contact hole 85.

Referring to FIG. 19 and FIG. 20, the dielectric layer 75, interposedbetween the intermediary layer 71 as the capacitive electrode and thecapacitive line 300, may be formed of a silicon oxide layer, such as anHTO (High Temperature Oxide) layer or an LTO (Low Temperature Oxide)layer, or a silicon nitride layer, each of which layers has a relativelythin thickness falling within a range from 5 to 200 nm. To increase thecapacitance of the storage capacitor 70, the thinner the dielectriclayer 75 is, the better it is as long as layer reliability is assured.

The capacitive line 300 extends from the image display area, where thepixel electrode 9 a is arranged, to the periphery of the pixel electrode9 a. The capacitive line 300 is electrically connected to a constantvoltage power source to be fixed to a constant potential. The constantvoltage power source may be a positive voltage power source or anegative voltage power source for supplying power to a scanning linedriving circuit, to be discussed later, which supplies the scanning line3 a with a scanning signal for driving the TFT 30, and a data linedriving circuit, to be discussed later, for controlling a samplingcircuit which supplies the data line 6 a with an image signal. Theconstant voltage power source may be fixed to a constant voltagesupplied to the counter electrode 21 of the counter substrate 20.

Like the capacitive line 300, the lower light shield layer 400, theupper light shield layer 401, and the side wall light shield layer 402may extend from the image display area to its periphery and may beconnected to a constant voltage power source to control an adverseeffect on the TFT 30 arising from variations in the potential of thelower light shield layer 400, the upper light shield layer 401, and theside wall light shield layer 402.

The pixel electrode 9 a is electrically connected to the heavily dopeddrain region 1 e of the semiconductor layer 1 a via the intermediarylayer 71, and the contact holes 83 and 85. In this embodiment, inaddition to the function of the pixel-potential capacitive electrode ofthe storage capacitor 70, the intermediary layer 71 has the function ofconnecting the pixel electrode 9 a to the TFT 30. Even if an interlayerdistance is as long as 2000 nm or so, two relatively small diametercontact holes connected in series connect the pixel electrode 9 a to theTFT 30 in an excellent condition using the intermediary layer 71,preventing any technical difficulty such as of connecting the pixelelectrode 9 a to the TFT 30 using a single contact hole. The apertureratio of the pixel is thus increased. Etching through is preventedduring the opening of the contact hole.

Similarly, the data line 6 a is connected to the heavily doped sourceregion 1 d of the semiconductor layer 1 a via a intermediary layer 72,formed of the same conductive layer as that of the intermediary layer71, and the contact holes 181 and 182.

Referring to FIG. 19, the TFT array substrate 10 is provided with thepixel electrodes 9 a, and arranged on top of them is an alignment layer19 which has been subjected to a predetermined rubbing process. Thepixel electrode 9 a is fabricated of a transparent conductive film, suchas an ITO (Indium Tin Oxide) film. The alignment layer 19 is fabricatedof an organic thin film, such as a polyimide film.

The counter substrate 20 has a counter electrode 21 extending on theentire surface thereof, and an alignment layer 22 therebeneath that hasbeen subjected to a predetermined rubbing process. The counter electrode21 is fabricated of a transparent conductive film, such as an ITO film.The alignment layer 22 is fabricated of an organic film, such as apolyimide film.

An underlayer insulator 40 is arranged beneath the pixel switching TFT30. The underlayer insulator 40 is formed on the entire surface of theTFT array substrate 10. Besides the function of assuring interlayerinsulation between the lower light shield layer 400 and the TFT 30, theunderlayer insulator 40 has the function of preventing thecharacteristics of the pixel switching TFT 30 from being degraded bysurface irregularity of the TFT array substrate 10 caused during apolishing process or dirt left after a cleaning operation.

Arranged on the scanning line 3 a is the first interlayer insulator 41through which a contact hole 182 leading to the heavily doped sourceregion 1 d and a contact hole 83 leading to the heavily doped drainregion 1 e are opened.

The intermediary layer 71, the intermediary layer 72, and the capacitiveline 300 are formed on the first interlayer insulator 41. Arranged onthese layers are the second interlayer insulator 42 through which acontact hole 181 and the contact hole 85, respectively leading to theintermediary layer 72 and the intermediary layer 71, are opened.

The data line 6 a is arranged on the second interlayer insulator 42.Formed on the data line 6 a is the third interlayer insulator 43 throughwhich the contact hole 85 leading to the intermediary layer 71 isopened. The upper light shield layer 401 is formed on the thirdinterlayer insulator 43. Arranged on the upper light shield layer 401 isthe fourth interlayer insulator 44, through which the contact hole 85 isopened. The pixel electrode 9 a is deposited on the fourth interlayerinsulator 44 thus constructed.

In the third embodiment as described above, the elements and linesformed in the image display area of the TFT array substrate 10, such asthe TFT 30, the scanning line 3 a, the data line 6 a, the capacitiveline 300, and the storage capacitor 70, are three-dimensionally lightshielded by the lower light shield layer 400, the upper light shieldlayer 401, and the side wall light shield layer 402. The lower lightshield layer 400, the upper light shield layer 401, and the side walllight shield layer 402 prevent light rays entering the substratevertically or obliquely from above, returning light rays entering thesubstrate vertically or obliquely from below, and internally reflectedlight or multiple reflected light in response to these light rays, fromentering the channel region 1 a′, the lightly doped source region 1 b,and the lightly doped drain region 1 c of the TFT 30. Furthermore, asshown in FIG. 18, the non-aperture area of each pixel is accuratelydefined in a grid configuration by these light shield layers.

In accordance with the third embodiment, the electrically conductive,light shield layer 403 formed in the contact hole 85 reliably preventslight from entering into the vicinity of the contact hole 85 which issubject to light ingress. The contact hole 85 is allowed to open at acenter position between the TFT 30 and a TFT 30 adjoining the TFT 30 asshown in FIG. 18. Even if a slight degree of light ingress takes placethrough the contact hole 85, the light ingress point is spaced apartfrom the TFT 30 of interest, and most light is unable to reach the TFT30.

As a result, the third embodiment increases light tightness, and allowsthe TFT 30 with reduced leakage photocurrent leakage thereof to performcorrectly switching control on the pixel electrode 9 a under severeoperational conditions in which highintensity light and returning lightare present. The present invention thus presents a bright andhigh-contrast image.

In accordance with the third embodiment, the lower light shield layer400 is deposited on the bottom of the trench 10CV formed in the TFTarray substrate 10, and the upper light shield layer 401 is arrangedover the TFT 30 accommodated in the trench 10CV. The side wall lightshield layer 402 fills the groove extending from the upper light shieldlayer 401 to the lower light shield layer 400 outside the TFT 30.

The TFT 30 is reliably three-dimensionally light shielded in arelatively simple construction using a relatively simple manufacturingprocess such as an etching step and a film formation step as in themanufacturing method in the first embodiment. In the third embodiment,the upper light shield layer 401 and the side wall light shield layer402 may be integrally formed as in the first and the second embodiment.For example, the upper light shield layer 401 may be laminated to fillthe groove after the groove has been formed.

In the third embodiment, the light shield layer may be arranged on thecounter substrate 20 in an area thereof facing the contact hole 85. Inthis arrangement, light ingress in the vicinity of the contact hole 85is further reduced.

The semiconductor layer 1 a forming the pixel switching TFT 30 in thethird embodiment may be a non-monocrystal layer or a monocrystal layer.A known technique such as an alignment method may be applied for theformation of the monocrystal layer. With the semiconductor layer 1 aformed of a monocrystal layer, the performance of the peripheralcircuits is increased.

The electrooptical device of a fourth embodiment of the presentinvention is discussed, referring to FIG. 21. FIG. 21 is across-sectional view of the electrooptical device of the fourthembodiment, corresponding to the cross section at line E—E′ in FIG. 18.

In the fourth embodiment, as shown in FIG. 21, a trench 10CV′ formed inthe TFT array substrate 10 is deeper, the lower light shield layer 400is deposited on the bottom and the tapered side walls of the trench10CV′. An upper light shield layer 401′ is arranged covering the largetrench 10CV′. No side wall light shield layer is not arranged. The restof the construction of the fourth embodiment remains unchanged from thatof the third embodiment.

In accordance with the fourth embodiment, the TFT 30 and wiring arereliably three-dimensionally light shielded in a relatively simpleconstruction using a relatively simple manufacturing process.

By adjusting the depth of the trench 10CV′, the underlayer of the pixelelectrode 9 a in an area where the TFT 30 and the wiring are arranged,i.e., the surface of the fourth interlayer insulator 44′ is planarized.In this way, orientation defects of the liquid crystal attributed tosteps on the surface thereof are reduced.

The electrooptical device of a fifth embodiment of the present inventionis now discussed, referring to FIG. 22. FIG. 22 is a cross-sectionalview of the electrooptical device of the fifth embodiment, correspondingto the cross section taken along line E—E′ in FIG. 18.

Referring to FIG. 22, the fifth embodiment is different from the thirdembodiment in that no trench is formed in the TFT array substrate 10,and that a side wall light shield layer 402″ is deposited in a groovewhich is accordingly formed deeper. With no trench formed, the lowerlight shield layer 400″ is flat, and the presence of the layers from theunderlayer insulator 40″ to the data line 6 a to the upper light shieldlayer 401″ causes the surface of the fourth interlayer insulator 44″ tobe raised in a ridge. The rest of the construction of the fifthembodiment remains unchanged from that of the third embodiment. Althoughnot shown in FIG. 22, the fourth interlayer insulator 44″ is also raisedin a ridge along the scanning line 3 a .

In accordance with the fifth embodiment, the TFT 30 and the wiring arereliably three-dimensionally light shielded in a relatively simpleconstruction using a relatively simple manufacturing process.

The electrooptical embodiment of a sixth embodiment is discussed,referring to FIG. 23. FIG. 23 is a plan view of a plurality of pixelelectrodes diagrammatically showing the relationship between thepolarity of a driving voltage in each pixel and a generation area of atransverse electric field in an electrooptical device of the sixthembodiment of the present invention during a scanning line alternatingdriving operation.

Referring to FIG. 23(a), during the presentation of a n-th (n is anatural number) field video signal or frame video signal, the polarityof the liquid crystal driving voltage represented by + or − in eachpixel electrode 9 a is not inverted, and the pixel electrodes 9 a aredriven by the same polarity on a row by row basis. Referring to FIG.23(b), during the presentation of a (n+1)th field video signal or framevideo signal, the voltage polarity of the liquid-crystal driving voltagein the pixel electrodes 9 a is inverted, and during the presentation ofthe (n+1)-th field or frame video signal, the polarity of theliquid-crystal driving voltage represented by +or − in each pixelelectrode 9 a is not inverted, and the pixel electrodes 9 a are drivenby the same polarity on a row by row basis. The states shown in FIG.23(a) and FIG. 23(b) are repeated with the period of field and frame,and the device is driven in the scanning line alternating driving methodin this embodiment. As a result, in accordance with this embodiment, thedevice is free from the degradation of the liquid crystal through theapplication of the direct current while presenting an image with reducedcross talk and reduced flickering. The scanning line alternating drivingmethod outperforms the data line alternating driving method in thatalmost no vertical cross talk is presented, and the scanning linealternating driving method outperforms the dot alternating drivingmethod in that an area suffering from the transverse electric field issubstantially small.

Referring to FIG. 23(a) and FIG. 23(b), in the scanning line alternatingdriving method, the generation area C1 of the transverse electric fieldis always located in the spacing between pixel electrodes 9 a adjacentin a direction of columns (a Y direction).

In accordance with the sixth embodiment, as in the fifth embodiment, notrench is formed in the generation area C1 of the transverse electricfield present in the gap area between the pixels along the scanning line3 a. A ridge is formed on the underlayer beneath the pixel electrode 9a. In the gap area, between the pixels, along the data line 6 a, whereno transverse electric field takes place, a deep trench is formed in theTFT array substrate 10 as in the fourth embodiment to planarize theunderlayer beneath the pixel electrode 9 a.

In accordance with the sixth embodiment, the use of the scanning linealternating driving method prevents the electrooptical material frombeing degraded by the application of a direct current voltage, whilecontrolling cross-talk and flickering in a presented image. Thelongitudinal electric field is strengthened by raising the underlayer ina ridge beneath the pixel electrode 9 a in the generation area C1 of thetransverse electric field. The transverse electric field is thusrelatively weakened. This arrangement reduces the orientation defects ofthe liquid crystal due to the transverse electric field.

The underlayer beneath the pixel electrode 9 a is planarized by formingthe deep trench in the gap area where no transverse electric field takesplace. This arrangement reduces the orientation defect of the liquidcrystal due to the step in the underlayer beneath the pixel electrode 9a.

As a result, the operational fault attributed to the transverse electricfield in the electrooptical material such as a liquid crystal issubstantially reduced, while a high-contrast, high-quality and brightimage is thus presented.

When the data line alternating driving method is adopted instead of thescanning line alternating driving method, the longitudinal electricfield is strengthened in the gap area, between pixels, extending alongthe data line 6 a, namely, the generation area of the transverseelectric field. To this end, the underlayer extending along the dataline 6 a is raised in a ridge while the underlayer beneath the pixelelectrode 9 a extending along the scanning line 3 a is planarized. Whenthe dot alternating driving method is adopted, the underlayer beneaththe pixel electrode 9 a is raised in a ridge in the areas along thescanning line 3 a and the data line 6 a in order to strengthen thelongitudinal electric field in the gap areas between the pixelsextending along the scanning line 3 a and the data line 6 a, namely thegeneration area of the traverse electric field.

In the scanning line alternating driving method of this invention, thepolarity of the driving voltage may be inverted every row, every twoadjacent rows, or every plural number of adjacent rows. Similarly, thepolarity of the driving voltage may be inverted every column, every twoadjacent columns, or every plural number of adjacent columns in the dataline alternating driving method of the present invention. In the dotalternating driving method, the polarity of the driving voltage may beinverted every block composed of a plurality of pixel electrodes.

The general construction of the electrooptical device in each of theabove embodiments will now be discussed, referring to FIG. 24 and FIG.25. FIG. 24 is a plan view of the electrooptical device 100 withelements formed thereon, viewed from the counter substrate 20. FIG. 25is a cross-sectional view of the electrooptical device including thecounter substrate 20 taken along line H—H′ in FIG. 24.

Referring to FIG. 24, the TFT array substrate 10 is provided with asealing material 52 along the edge thereof, and a third light shieldlayer 53 as a display peripheral outline, fabricated of the samematerial as that of the light shield layer extends along the internaledge of the sealing material 52. A data line driving circuit 101 andexternal-circuit interconnect terminals 102 are arranged on one side ofthe TFT array substrate 10, being external to the area of the sealingmaterial 52, and scanning line driving circuits 104 are arranged on twosides adjacent to the one side of the TFT array substrate 10. If a delayin the scanning signal supplied to the scanning line 3 a presents noproblem, the scanning line driving circuit 104 may be mounted only onone side. Data line driving circuits 101 may be arranged on both sidesof the image display area. For instance, odd data lines 6 a may besupplied with the video signal by the data line driving circuit arrangedon one side of the image display area, and even data lines 6 a may besupplied with the video signal by the data line driving circuit arrangedon the opposite side of the image display area. If the data lines 6 aare driven in such an interdigital fashion, the formation area of thedata line driving circuits 101 is expanded, and a complex circuit may beincorporated therewithin. Arranged on the remaining one side of theimage display area of the TFT array substrate 10 is a plurality of wire105 for connecting the scanning line driving circuits 104 mounted on theboth sides of the image display area. A conductive material 106 forelectrically connecting the TFT array substrate 10 to the countersubstrate 20 is mounted at least at one corner of the counter substrate20. Referring to FIG. 25, the counter substrate 20 having almost thesame outline as that of the sealing material 52 shown in FIG. 24 isbonded to the TFT array substrate 10 through the sealing material 52.

Besides the data line driving circuits 101 and the scanning line drivingcircuit 104, the TFT array substrate 10 may be provided with a samplingcircuit for applying the video signal to the plurality of the data lines6 a at a predetermined timing, a precharge circuit for supplying aprecharge signal at a predetermined voltage level to the plurality ofthe data lines 6 a prior to the application of the video signal, and atest circuit for checking the quality and defects of the electroopticaldevice in the middle of the production or at the shipment thereof. Thesampling circuit, the precharge circuit, and the test circuit may bearranged in an area beneath the light shield layer 53.

In each of the above-referenced embodiments, the data line drivingcircuit 101 and the scanning line driving circuit 104 may beelectrically and mechanically connected to a driver LSI mounted on a TAB(Tape Automated Bonding board), through an anisotropically electricallyconductive film arranged in the vicinity of the TFT array substrate 10,instead of mounting the data line driving circuit 101 and the scanningline driving circuit 104 on the TFT array substrate 10. Arranged on thelight incident side of the counter substrate 20 and the light exit sideof the TFT array substrate 10 are respectively polarizer films,retardation films, and polarizer means in predetermined directions towork with operation modes of the liquid crystal 50 such as a TN (twistednematic) mode, a VA (Vertically Aligned) mode, or a PDLC (PolymerDispersed Liquid Crystal) mode, and normally white mode/normally blackmodes.

The electrooptical device thus constructed may be used in aprojection-type display apparatus (a liquid-crystal projector). Threepanels of the electrooptical devices 100 are used as RGB light valves,and each light valve receives each color light separated through RGBcolor separating dichroic mirrors. In each of the above embodiments, theelectrooptical device 100 is equipped with no color filter. Optionally,an RGB color filter may be arranged in a predetermined area facing thepixel electrode 9 a, on the counter substrate 20 along with a protectivefilm. In this way, the liquid-crystal display device of each embodimentfinds applications in a direct viewing or reflective type colorliquid-crystal television, besides the liquid-crystal projector.Microlenses may be arranged on the counter substrate 20 on a onemicrolens per pixel basis. A color filter layer may be formed of a colorresist beneath the pixel electrodes 9 a facing the RGB on the TFT arraysubstrate 10. In this way, condensation efficiency of the incident lightis increased, and a liquid-crystal display device provides a brightimage. By laminating interference layers having different refractiveindexes on the counter substrate 20, a dichroic filter for creating theRGB colors is formed taking advantage of interference of light. Thecounter substrate with such a dichroic filter allows a liquid-crystaldisplay device to provide an even brighter image.

An example of the pixel switching TFT used in each pixel is a positivestagger type or coplanar type polysilicon TFT as explained earlier.Other types of TFTs including a reverse stagger type TFT or an amorphoussilicon TFT may be used for other pixel switching TFT.

Discussed next is an embodiment of a projection-type color displayapparatus as one example of electronic equipment incorporating theabove-referenced electrooptical device as a light valve as shown in FIG.26 and FIG. 27.

Referring to FIG. 26, the circuit arrangement of the projection-typecolor display apparatus of this embodiment will now be discussed. FIG.26 shows the circuit arrangement of one of the three light valves in theprojection-type color display apparatus. Since the three light valvesbasically have the same structure, only one of these valves isdiscussed. Precisely speaking, however, the three light valves aredriven by different input signals (namely, R, G, and B signals).Furthermore, the circuit arrangement of the G light valve changes theorder of the video signal to be presented in reverse order within eachfield or each frame, in comparison with the R and B video signals, orreverses the direction of the horizontal scanning or the verticalscanning.

As shown in FIG. 26, the projection-type color display apparatusincludes a display information output source 1000, a display informationprocessing circuit 1002, a drive circuit 1004, the above liquid crystaldevice 100, a clock generator circuit 1008, and a power source circuit1010. The display information output source 1000 can include a memory,such as a ROM (Read Only Memory), a RAM (Random Access Memory), or anoptical disk, and a tuning circuit for outputting a video signal bytuning to the video signal, and outputs, to the display informationprocessing circuit 1002, display information such as a video signal in apredetermined format in response to a clock signal from the clockgenerator circuit 1008. The display information processing circuit 1002can include a variety of known processing circuits, such as an amplifierand polarity reversal circuit, a serial-to-parallel converter circuit, arotation circuit, a gamma correction circuit, and a clamp circuit, andsuccessively generates a digital signal from display information inputin response to the clock signal, and then outputs, to the drive circuit1004, the digital signal along with the clock signal CLK. The drivecircuit 1004 also drives the liquid crystal device 100. The power sourcecircuit 1010 supplies predetermined power to each of the above circuits.The driving circuit 1004 may be mounted on the TFT array substrate ofthe electrooptical device 100, and further, the display informationprocessing circuit 1002 may also be mounted on the TFT array substrate.

Referring to FIG. 27, the general construction of the projection-typecolor display apparatus of this embodiment will now be discussed (fromthe standpoint of optical structure). FIG. 27 is a diagrammaticcross-sectional view of the projection-type color display apparatus.

Referring to FIG. 27, a liquid-crystal projector 1100 as one example ofthe projection-type color display apparatus of this embodiment includesthree liquid-crystal modules, each including the electrooptical device100 having the driving circuit 1004 on the TFT array substrate. Theliquid-crystal projector 1100 thus includes light valves 100R, 100G, and100B for RGB colors. When light is emitted from a lamp unit 1102 as awhite light source such as a metal halide lamp in the liquid-crystalprojector 1100, the light is separated into three RGB color beamsthrough three mirrors 1106 and two dichroic mirrors 108, and the threecolor light beams are then guided to respective light valves 100R, 100G,and 100B. The blue color beam travels along a path longer than those forthe red and green color beams, and to prevent loss, the blue color beamis guided through a relay lens system 1121, including an incident lens1122, a relay lens 1123, and an exit lens 1124. The red, green, and bluelight beams respectively color-modulated by the light valves 100R, 100G,and 100B are incident on a dichroic prism 1112, thereby synthesizing thethree color images, and a synthesized color image is then projected by aprojection lens 1114 onto a screen 1120.

An electrooptical device of the present invention assures lighttightness, and presents a bright, high-quality image. The electroopticaldevice of the present invention may be used as a display apparatusincluding a display area of a variety of electronic equipment, besides aprojection-type display apparatus, such as a liquid crystal displaytelevision, a viewfinder type or direct monitoring type video cassetterecorder, a car navigation system, an electronic pocketbook, anelectronic tabletop calculator, a word processor, a workstation, amobile telephone, a video phone, a POS terminal, and an apparatus havinga touch panel.

The present invention is not limited to the above-referencedembodiments, and modifications are possible within the scope of thepresent invention as in the claims and the specification, and theelectrooptical device, the projection-type display apparatus, and themethod of manufacturing the electrooptical device, with suchmodifications accordingly fall within the spirit and scope of thepresent invention.

What is claimed is:
 1. An electrooptical device, comprising: a firstsubstrate; a pixel electrode arranged above the first substrate; athin-film transistor arranged above the first substrate and connected tothe pixel electrode; and a first light shield layer arranged over a gateelectrode of the thin-film transistor formed over and facing a channelregion of the thin-film transistor with a gate insulator disposedtherebetween, the first light shield layer being formed of a conductivelayer; and the first light shield layer being formed laterallysurrounding the channel region as a light shield side portion.
 2. Theelectrooptical device according to claim 1, further comprising a secondsubstrate opposed to the first substrate, and an electrooptical materialdisposed between the first substrate and the second substrate.
 3. Theelectrooptical device according to claim 1, wherein a matrix of thepixel electrodes and the thin-film transistors are arranged on the firstsubstrate.
 4. The electrooptical device according to claim 1, whereinthe light shield side portion is formed of the first light shield layerformed in a light shield side portion formation trench formed in atleast one insulator below the first light shield layer.
 5. Theelectrooptical device according to claim 1, wherein a drain electrode,formed over a drain region of the thin-film transistor, is electricallyconnected to the drain region of the thin-film transistor, the pixelelectrode, formed over the drain electrode, is electrically connected tothe drain electrode, and the drain electrode is fabricated of aconductive layer having a light shield property formed over and coveringthe channel region.
 6. The electrooptical device according to claim 5,wherein the drain electrode and the first light shield layer form astorage capacitor with an insulator, as a dielectric layer, disposedbetween the drain electrode and the first light shield layer.
 7. Theelectrooptical device according to claim 1, wherein a data line, formedover a source region of the thin-film transistor, is electricallyconnected to a source region of the thin-film transistor, and the dataline is fabricated of a conductive layer having a light shield propertyand covering the channel region from above.
 8. The electrooptical deviceaccording to claim 7, wherein an active layer of the thin-filmtransistor is formed of a semiconductor layer that is arranged beneaththe data line and within a formation area of the data line.
 9. Theelectrooptical device according to claim 7, wherein the data lineextends in a line having generally uniform width.
 10. The electroopticaldevice according to claim 1, wherein a second light shield layer isformed beneath and covering the channel region.
 11. The electroopticaldevice according to claim 10, wherein the first light shield layer isrouted through the side portion formation trench and is electricallycoupled to the second light shield layer.
 12. The electrooptical deviceaccording to claim 11, wherein the first light shield layer is directlycoupled to the second light shield layer.
 13. The electrooptical deviceaccording to claim 12, wherein the first light shield layer is formed inthe side portion formation trench, reaching a bottom of the side wallformation trench.
 14. The electrooptical device according to claim 11,wherein the first light shield layer is connected to the second lightshield layer through another conductive layer having a light shieldproperty.
 15. The electrooptical device according to claim 14, whereinin the side wall formation trench, a conductive layer fabricated of thesame material as the conductive layer forming the gate electrode, isdeposited on the bottom of the side portion formation trench, and thelight shield side portion is formed on the conductive layer.
 16. Aprojection-type display apparatus, comprising: a light valve including afirst substrate, a pixel electrode arranged above the first substrate, athin-film transistor arranged above the first substrate and coupled tothe pixel electrode, and a first light shield layer arranged over a gateelectrode of the thin-film transistor formed over and facing a channelregion of the thin-film transistor with a gate insulator disposedtherebetween, and the first light shield layer being formed of aconductive layer, wherein the first light shield layer is formedlaterally surrounding the channel region as a light shield side portion;a light source that directs light to the light valve; and an opticalsystem for projecting a light beam from the light valve.
 17. A methodfor manufacturing an electrooptical device including a first substrate,a pixel electrode arranged on the first substrate, and a thin-filmtransistor arranged on the first substrate and coupled to the pixelelectrode, the method comprising: forming, on the surface of the firstsubstrate, the thin-film transistor including a channel region, a gateinsulator formed on the channel region, and a gate electrode on the gateinsulator, with the gate electrode facing the channel region with thegate insulator disposed therebetween, depositing at least one interlayerinsulator covering the thin-film transistor subsequent to the formationof the thin-film transistor, forming, in the interlayer insulator, aside portion formation trench that extends along the side of the channelregion of the thin-film transistor, and depositing a first light shieldlayer covering at least the channel region of the thin-film transistor,wherein the first light shield layer is also deposited in the sideportion formation trench as a light shield side portion when the firstlight shield layer is formed.
 18. The method for manufacturing anelectrooptical device according to claim 17, further comprising:depositing, on the surface of the first substrate, a second light shieldlayer, an underlayer insulator, a semiconductor layer forming thethin-film transistor, and the gate insulator of the thin-filmtransistor, prior to formation of the thin-film transistor on thesurface of the first substrate, forming a connection trench in the gateinsulator and the underlayer insulator, extending along the channelregion of the thin-film transistor and extending to the second lightshield layer, and then depositing a conductive layer, which also formsthe gate electrode, in the connection trench when the gate electrode isformed, depositing the interlayer insulator on the gate electrode, andthen, forming the side portion formation trench communicating and beingintegral with the connection trench when the side portion formationtrench is formed, and forming the first light shield layer, wherein whenthe first light shield layer is deposited, the first light shield layeralso extends in the side portion formation trench to form the lightshield side wall connected to the conductive layer in the side portionformation trench.
 19. The method for manufacturing an electroopticaldevice according to claim 17, comprising: depositing, on the surface ofthe first substrate, a second light shield layer, an underlayerinsulator, a semiconductor layer forming the thin-film transistor, thegate insulator of the thin-film transistor, and the gate electrode ofthe thin-film transistor, prior to the formation of the thin-filmtransistor on the surface of the first substrate; depositing theinterlayer insulator over the gate electrode; forming the side portionformation trench in the interlayer insulator, the gate insulator, andthe underlayer insulator, extending along the channel region of thethin-film transistor and extending to the second light shield layer; andforming the first light shield layer, wherein when the first lightshield layer is deposited, the first light shield layer also extends inthe side portion formation trench to form the light shield side portionconnected to the second light shield layer in the side portion formationtrench.